The correct answer is C. both viscosity and unit weight.
Permeability is the ability of a porous material to allow fluids to flow through it. The physical properties of a permeant that influence permeability are viscosity and unit weight.
Viscosity is a measure of the resistance of a fluid to flow. The higher the viscosity, the more resistance there is to flow. This means that fluids with high viscosity will have lower permeability than fluids with low viscosity.
Unit weight is a measure of the weight of a unit volume of a material. The higher the unit weight, the more weight there is per unit volume. This means that materials with high unit weight will have lower permeability than materials with low unit weight.
The following is a brief explanation of each option:
- Option A: Viscosity only. This is incorrect because unit weight also influences permeability.
- Option B: Unit weight only. This is incorrect because viscosity also influences permeability.
- Option C: Both viscosity and unit weight. This is the correct answer because both viscosity and unit weight influence permeability.
- Option D: None of the above. This is incorrect because both viscosity and unit weight influence permeability.